1. Field
Disclosed herein are soft magnetic alloy compositions containing iron, cobalt, vanadium and niobium with low amounts, if any, of carbon. Also disclosed herein are methods for manufacturing such soft magnetic alloys. Also disclosed are annealed alloys of the composition noted above and having high yield strengths and magnetic properties suitable for rotating electrical devices, wherein the yield strength can be adjusted by varying the annealing temperature.
2. Description of Related Art
A ferromagnetic material that can be magnetized, but tends not to remain magnetized is described as magnetically soft. When a magnetically soft material is magnetised in a magnetic field and then removed from the magnetic field, it loses most of the magnetism exhibited while in the field. A magnetically soft material preferably displays a low hysteresis loss, high magnetic permeability and a high magnetic saturation induction. Magnetically soft materials are used in various static and rotating electrical devices, such as motors, generators, alternators, transformers and magnetic bearings.
U.S. Pat. No. 5,501,747 discloses a high strength, soft magnetic iron-cobalt-vanadium based alloy which further comprises 0.15 weight percent to 0.5 weight percent niobium and 0.003 weight percent to 0.02 weight percent carbon. This alloy is disclosed as having a combination of yield strength, magnetic properties and electrical properties which enables it to be used for the rotating part, such as a rotor, of a rotating electrical machine. When the alloy is annealed at a temperature of not more than about 740° C. for not more than about 4 hours, it has a room temperature yield strength of at least 620 MPa.
However, further soft magnetic alloys having a combination of a high yield strength and magnetic properties suitable for applications, such as rotating electrical devices, are desirable.